Typically, a wafer board panel comprises layers of wood flakes or wafers formed into a composite structure using a resinous binder. The preparation of wafer board panels is complex, but broadly consists of two principal stages. The first stage comprises the preparation of the wafers and the admixing thereof to form a loose layer or mat The second stage involves subsequent compression and heating of the mat to cure the resin and form the consolidated panel.
Until recently, wafer board was manufactured in the form of planar or flat sheets. However, as disclosed in U.S. Pat. No. 4,616,991, the present applicant has developed an apparatus and process for the manufacture of panels having a wave-like or corrugated configuration. Such wave-board panels have improved structural strength properties, relative to planar panels.
This prior patented apparatus involved a pair of opposed, spaced-apart, upper and lower platens. Each platen was formed of adjacent lengths of chain-like links. When the lengths were pushed inwardly from the side, they would shift from a planar to an undulating corrugated form.
The process steps involved:
distributing a mat of loose wood wafers between the upper and lower platen surfaces while they were maintained in the planar configuration; PA1 biasing the platens together to pre-compress the mat, and thereby substantially fixing the wafers together to limit their further relative movement; PA1 converting the two platen surfaces, still in pressing association with the mat, from the planar to the corrugated configuration; and PA1 then applying additional pressure and heat for a sufficient time to cure the binder and produce a corrugated sandwich wave-board panel. PA1 utilizing corrugated platens like those described in the '991 patent i.e. platens which are mechanically convertible between a planar and a corrugated configuration; PA1 placing the metal sheet to be used metal on the lower press platen; PA1 distributing the mat of loose wood wafers in admixture with an isocyanate resin onto the overlay sheet; PA1 optionally placing a second sheet of overlay over the mat; PA1 biasing the platens together to pre-compress the mat substantially fixing the wafers so as to limit their relative movement and bringing the metal sheet into contact therewith; PA1 converting the two platen surfaces, still in pressing association with the mat and the metal sheet, from the planar to the corrugated configuration so as to translate both the metal sheet and mat in combination in a single stage from the planar to the corrugated metal-clad form; and PA1 applying additional pressure (and optionally heat) so as to cure the binder and provide a cohesive corrugated metal-clad sandwich wave-board panel.
The main advantage inherent in the patented process was that the panel product so formed was characterized by having a substantially uniform density. This was achieved because the wafers were fixed by the pre-compression step and because the mat was not significantly stretched or elongated during the conversion from the planar to the corrugated configuration.
It would be an advantage if one could provide a corrugated metal-clad sandwich panel. By metal clad is meant with a metal sheet cohesive with the wafer board core on at least one face thereof. The metal-clad panel would find use in high moisture-exposure applications (i.e. roof sheeting or the like).